The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to produce over-voltage and voltage transient protection circuits that could be used to protect various types of devices such as voltage regulators. These over-voltage and voltage transient protection circuits generally included a linear regulator that used a pass transistor and an operational amplifier to control an output voltage. During a transient or over-voltage event, the over-voltage protection circuit generally disabled the linear regulator and prevented regulation until the transient or over-voltage condition was eliminated. Because the linear regulator was disabled, the linear regulator did not provide over-voltage protection and additional circuitry was required. Usually, a zener diode was coupled between the input and ground to help protect against input over-voltage conditions. However, the voltage at which the zener diode conducted was not very accurate or very controlled, thus, the voltage applied to the output could exceed the desired maximum value of the output voltage. One example of such a transient protection circuit is described in U.S. Pat. No. 4,008,418 that issued on Feb. 15, 1997 that issued to Howard E. Murphy.
Accordingly, it is desirable to have a protection circuit that more accurately regulates the output voltage, that minimizes overshoots during a transient, and that has a faster reaction time.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.